1. Field
The present invention relates to a compound tube and a method of producing the same. For example, the compound tube includes an inner tube and an outer tube. A passage is formed inside of the inner tube, and another passage is formed between the inner tube and the outer tube.
2. Description of Related Art
Japanese Patent Publication No. A-2002-318015 discloses a refrigerant-reheating tube as a compound tube, in which an inner tube is inserted into an outer tube. Ends of the outer tube are coupled to an external surface of the inner tube. In the compound tube, either one of high-temperature refrigerant and low-temperature refrigerant flows in the inner tube, and the other refrigerant flows between the inner tube and the outer tube. Thus, heat is exchanged between the high-temperature refrigerant and the low-temperature refrigerant.
However, a specific method of coupling the inner tube and the outer tube is not described in Japanese Patent Publication No. A-2002-318015. Thus, an accurate and reliable method of coupling the inner tube and the outer tube is needed to thereby reduce leakage of the refrigerants and to improve manufacturability.